A water extinguisher is contraindicated for a fire involving _____.

A water extinguisher is contraindicated for a fire involving _____.

• A. electrical equipment fire
• B. wood and paper fire
• C. metal fires
• D. restaurant cooking oil fire

Answer: (D)

Grease fires require a different approach than ordinary combustibles. Water-based extinguishers are not suitable for cooking oil fires because oil and water don’t mix and the oil sits on top of the water. When water contacts hot oil, it sinks to the bottom, instantly flashes to steam, and drives burning oil into a rapid boilover. That steam pressure and splattering can scatter flames and make the fire bigger instead of putting it out. The cooling effect of water doesn’t help here, since the oil continues to burn and can reignite once the water evaporates. The safer option is to use a extinguisher labeled for grease fires (wet chemical or dry chemical designed for Class K/B grease fires) or to smother the flames with a metal lid or fire blanket if it’s feasible and safe. Avoid pouring water on kitchen oil fires.

Grease fires require a different approach than ordinary combustibles. Water-based extinguishers are not suitable for cooking oil fires because oil and water don’t mix and the oil sits on top of the water. When water contacts hot oil, it sinks to the bottom, instantly flashes to steam, and drives burning oil into a rapid boilover. That steam pressure and splattering can scatter flames and make the fire bigger instead of putting it out. The cooling effect of water doesn’t help here, since the oil continues to burn and can reignite once the water evaporates.

The safer option is to use a extinguisher labeled for grease fires (wet chemical or dry chemical designed for Class K/B grease fires) or to smother the flames with a metal lid or fire blanket if it’s feasible and safe. Avoid pouring water on kitchen oil fires.